1. Field of the Invention
The present invention relates to a laser beam guiding fiber, and in particular, relates to a laser beam guiding fiber for the use in, for example, a catheter for lasing in which laser beam irradiation cures a lesion portion.
2. Description of Related Art
Catheters for the use of lasing have been developed which removes a lesion portion such as a thrombus in a blood vessel, which a practitioner cannot directly approach, by means of irradiating with a laser beam and heat-vaporizing the portion. In such the lasing catheter, an optical fiber (a laser beam guiding fiber) is used to guide the laser beam to a tip of the catheter.
With the use of a conventional laser beam guiding fiber, since radiated light is in the form of thin beam in order to increase an irradiated energy density, there exists a following problem, for example, in the case of treating the lesion portion, such as an obstructed portion in the blood vessel in which it is difficult for the tip of the catheter to move widely.
That is, when the lesion portion would be irradiated with the laser beam widely in the case where such the lesion portion extends widely, the tip of the laser beam guiding fiber should be apart from the lesion portion, so that the irradiating energy density of the laser beam would be reduced. Therefore, it is necessary to increase an amount of the laser beam energy which enters the laser beam guiding fiber in order to irradiate the lesion portion with a sufficient amount of energy. However, when the amount of the laser beam energy is increased, the laser beam guiding fiber tends to be destroyed by the energy of the laser beam.